matrix_reload.cpp

#include <iostream>
using namespace std;
class matrix
{
public:
	matrix(int, int);
	matrix(double**, int, int);
	matrix(const matrix&);
	~matrix();
	friend  matrix  operator+(const matrix&, const matrix&);
	matrix& operator=(const matrix &);
	friend ostream& operator<<(ostream& output, const matrix&);
	friend istream& operator>>(istream& input, matrix&);
private:
	int m, n;
	double** a;
};

matrix::matrix(int m, int n)
{
	this->m = m; this->n = n;
	a = new double*[m];
	for (int i = 0; i < m; i++)
	{
		a[i] = new double[n];
	}
}

matrix::matrix(const matrix& M) {
	this->m = M.m; this->n = M.n;
	this->a = new double*[m];
	for (int i = 0; i < m; i++)
	{
		this->a[i] = new double[n];
	}
	for (int i = 0; i < m; i++) {
		for (int j = 0; j < n; j++)
			this->a[i][j] = M.a[i][j];
	}
}

matrix::matrix(double** T, int m, int n)
{
	this->m = m; this->n = n;
	a = T;
}

matrix::~matrix()
{
	for (int i = 0; i < m; i++)
	{
		if (a[i] != NULL)
		{
			delete[]a[i];
			a[i] = NULL;
		}
	}
	delete[]a;
	a = NULL;
}
matrix& matrix::operator=(const matrix & A)
{
	m = A.m; n = A.n;
	for (int i = 0; i < A.m; i++)
	{
		for (int k = 0; k < A.n; k++)
		{
			a[i][k] = A.a[i][k];
		}
	}
	return *this;
	// TODO: 在此处插入 return 语句
}


matrix   operator+(const matrix& A, const matrix& B)
{
	matrix C(A.m, A.n);
	/*double** T;
	T = new double* [A.m];
	for (int i = 0; i < A.m; i++)
	{
		T[i] = new double[A.n];
	}*/
	for (int i = 0; i < A.m; i++)
	{
		for (int k = 0; k < A.n; k++)
		{
			C.a[i][k] = A.a[i][k] + B.a[i][k];
			//T[i][k] = A.a[i][k] + B.a[i][k];
		}
	}
	const matrix D = C;
	return D; //不能像注释部分这样写，因为一旦出了函数就会调用析构函数，就会导致赋值时出错！！！（找不到指针）
	//return matrix(T, A.m, A.n); //此处重载了构造函数

}

ostream& operator<<(ostream& output, const matrix& A)
{
	for (int i = 0; i < A.m; i++)
	{
		for (int k = 0; k < A.n; k++)
		{
			cout << A.a[i][k] << "  ";
		}
		cout << endl;
	}
	return output;
	// TODO: 在此处插入 return 语句
}

istream& operator>>(istream& input, matrix& A)
{

	for (int i = 0; i < A.m; i++)
	{
		for (int k = 0; k < A.n; k++)
		{
			cin >> A.a[i][k];
		}
	}
	return input;
	// TODO: 在此处插入 return 语句
}
int main()
{
	int m, n;
	cout << "enter m: "; cin >> m; cout << "enter n: "; cin >> n;
	matrix A(m, n); cout << "Please enter this " << m << " x " << n << " matrix" << endl; cin >> A;
	matrix B(m, n); cout << "Please enter this " << m << " x " << n << " matrix" << endl; cin >> B;
	cout << "C=A+B=" << endl;
	matrix C(m, n);
	C = (A + B);
	cout << (A + B) << endl;
}